The present invention relates to an input circuit of a counter circuit used in a frequency synthesizer IC (integrated circuit). More specifically, the present invention relates to an input circuit of a counter circuit and to an integrated circuit for a frequency synthesizer using the same. The input circuit is capable of being connected as it is in both 1) where signals of two frequency bands which are away from each other such as the AM (amplitude-modulated) band and the FM (frequency-modulated) band are output from one output terminal and b) where the signals are separately output from two output terminals.